Calories to Joules Converter
Convert calories to joules — one calorie is 4.184 joules, and mind which calorie you mean. Results update as you type; exact factors shown.
One calorie (thermochemical) is 4.184 joules — see the exact factor, not a rounded rule of thumb.
How the calories to joules converter works
Energy converts through the joule. A thermochemical calorie is exactly 4.184 J, so a food Calorie (kcal) is 4.184 kJ. A kilowatt-hour is exactly 3.6 MJ. A BTU is 1,055.056 J and a US therm is 100,000 BTU.
The US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common energy conversions
| From | To | Units |
|---|---|---|
| 1 cal | 4.184 J | calorie (thermochemical) to joules |
| 10 cal | 41.84 J | calorie (thermochemical) to joules |
| 50 cal | 209.2 J | calorie (thermochemical) to joules |
| 100 cal | 418.4 J | calorie (thermochemical) to joules |
| 250 cal | 1,046 J | calorie (thermochemical) to joules |
| 500 cal | 2,092 J | calorie (thermochemical) to joules |
| 1,000 cal | 4,184 J | calorie (thermochemical) to joules |
| 2,000 cal | 8,368 J | calorie (thermochemical) to joules |
| 2,500 cal | 10,460 J | calorie (thermochemical) to joules |
| 5,000 cal | 20,920 J | calorie (thermochemical) to joules |
| 10,000 cal | 41,840 J | calorie (thermochemical) to joules |
| 100,000 cal | 418,400 J | calorie (thermochemical) to joules |
Units in this converter and their exact factors
| Unit | Symbol | One unit in joules |
|---|---|---|
| joule | J | 1 joule |
| kilojoule | kJ | 1,000 joule |
| megajoule | MJ | 1,000,000 joule |
| calorie (thermochemical) | cal | 4.184 joule |
| kilocalorie (food Calorie) | kcal | 4,184 joule |
| watt-hour | Wh | 3,600 joule |
| kilowatt-hour | kWh | 3,600,000 joule |
| British thermal unit | BTU | 1,055.05585262 joule |
| therm (US) | thm | 105,505,585.262 joule |
| foot-pound | ft·lb | 1.3558179483 joule |
FAQFrequently asked questions about energy conversion
How many joules in a calorie?
4.184 J for the small calorie used in physics.
Is a food Calorie the same?
No — a food Calorie is a kilocalorie, a thousand of these, so 4,184 J.
How much energy is a 2,000 Calorie diet?
About 8.4 million joules, or 8,368 kJ.
Why do labels use kJ?
Because it is the SI unit; many countries print both kJ and kcal.
How do I convert kcal to kJ?
Multiply by 4.184.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.